1. Field of Invention
The present invention relates to mixing gases for use as breathing gas.
2. Description of Prior Art
There have been apparatus or systems in the prior art for mixing oxygen with one or more gases for breathing purposes. Examples are U.S. Pat. Nos. 3,534,753; 2,818,860; 3,727,627; 3,669,134; 3,598,134; 3,762,427; and 3,762,428. For the most part, these systems were intermittent or "demand" systems--the gases were mixed together in proportions in response to use of the end product mixed gas. Thus, the gases were mixed in their final proportions as a single event each time there was use of the end product. Since the gases being mixed in these systems were not reactive with each other, an attempt to use them with reactive gases could result in a sustained fire which was continuously fed by incoming reactive gases or an explosion. Further, if flow rates became low, back diffusion of one reactive gas into the other caused a hazardous situation.
It has been proposed to use hydrogen as the mixing gas for oxygen for supply to divers and pressure chambers, particularly to hyperbaric pressures or for use at great depths. However, these two gases are so mutually reactive, unless their relative mixture was precisely and constantly controlled that mere turning on or off of the system could cause explosion.